1. Field of the Invention
This invention relates to enlargement photographing apparatuses and, more particularly, to an enlargement photographing apparatus for changing a relative distance between photographing lenses and a camera body.
2. Related Art And Prior Art Statement
Conventionally, close-up photographing and enlargement photographing by the use of a camera of a single-lens reflex system are performed by insertion of a light-shielded or shaded intermediate device between a camera body and photographing lenses, as disclosed in, for example, Japanese Patent Laid-Open No. HEI 2-48612 or Japanese Patent Laid-Open No. HEI 2-48613. As the intermediate device, a bellows type device is used for connecting a mounting portion on the side of the camera and a mounting portion on the side of the photographing lenses by means of a bellows in an extendible and retractable manner, an intermediate ring with which a ring set to a constant or predetermined length is combined, or the like.
The above-described close-up photographing is performed between about 0.2 times to about 12 times of a photographing magnification or scale factor, and is realized by the fact that a length of the intermediate ring or the like for lenses of a focal distance in accordance with each of the photographing scale factors is changed. Further, display of these photographing scale factors is mechanically performed on the photographing lenses.
FIG. 11A, FIG. 11B and FIG. 11C of the attached drawings are correlation model figures between a feeding quantity d of conventional photographing lenses and a photographing scale factor .beta..
In these figures, the reference character L denotes a photographing lens having a focal distance or length f; F, a film surface serving as an image-formation or imaging surface; H.sub.0, a subject; H, an imaged image; a, a subject distance (a distance between the photographing lenses L and the subject H.sub.0); b, an image distance (a distance between the photographing lenses L and the imaging surface F); and 1, a photographing distance (a distance between the subject H.sub.0 and the imaging surface F).
FIG. 11A shows the time at which the quantity of feeding d of the photographing lenses L is zero, and illustrates a case where a focal point of the lens L is located at the imaging surface F so that the photographing scale factor .beta.=1/.infin..
FIG. 11B and FIG. 11C show a state under which the lens L is fed. FIG. 11B shows the time at which the photographing scale factor .beta. is substantially one time, while FIG. 11C shows the time at which the photographing scale factor .beta. is two times.
Moreover, the photographing scale factor .beta., the photographing distance 1 and the subject distance a can be expressed by the following relationship: EQU .beta.=H/H.sub.O =b/a=d/f (1) EQU 1=f+(1+.beta.).sup.2/.beta. ( 2) EQU a =f(1+1/.beta.) (3)
From the above equation (1), since the photographing scale factor .beta. is in proportion to the quantity of feeding of the lens d, the quantity of feeding of the lens d is adjusted to obtain a desired photographing scale factor .beta.. As a matter of fact, the aforesaid length of the intermediate device between the camera and the photographing lenses is adjusted. However, it becomes troublesome to find d from the above equation (1) every time thereof. Accordingly, generally, d is found from a table in which the relationship between the photographing scale factor and the quantity of feeding which are attached to the close-up lens is previously calculated or computed as shown in Table 1 so that the length is adjusted while reading a scale or graduation or the like which is provided on the intermediate device.
TABLE 1 __________________________________________________________________________ range of length subject subject fully of subject distance coming out bellows distance from the on film image lens from forward surface exposure scale feeding graduation film end of (short side .times. scale factor quantity of scale surface lens barrel long side) factor __________________________________________________________________________ 1.81 3.6 cm 68 mm 16.2 cm 4.6 cm 13.2 .times. 7.9 .times. 19.8 mm 2.0 4.2 75 16.7 4.4 12.0 .times. 9.0 .times. 18.0 2.2 5.0 83 17.3 4.3 10.9 .times. 10.2 .times. 16.4 2.4 5.8 90 17.9 4.1 10.0 .times. 11.6 .times. 15.0 2.6 6.5 98 18.5 4.0 9.2 .times. 13.0 .times. 13.8 2.8 7.3 106 19.2 3.9 8.6 .times. 14.4 .times. 12.9 3.0 8.0 113 19.9 3.8 8.0 .times. 16.0 .times. 12.0 3.5 9.9 132 21.6 3.6 6.9 .times. 20.3 .times. 10.3 4.0 11.8 151 23.3 3.5 6.0 .times. 25.0 .times. 9.0 __________________________________________________________________________ Macro-lens 38 mm F3.5
Meanwhile, as an enlargement photographing apparatus capable of changing a photographing scale factor by means of a motor, disclosed in Japanese Patent Laid-Open No. HEI 3-223804 or Japanese Patent Laid-Open No. HEI 3-223817 is technical means in which the motor is built into macro-photographing lenses, the motor is angularly moved by a scale-factor changing operation to change a distance between a camera body and photographing lenses, and scale-factor changing information is transmitted from a ROM built into the photographing lenses at the side of a camera body.
For the technical means disclosed in Japanese Patent Laid-Open No. HEI 2-48612 or Japanese Patent Laid-Open No. HEI 2-48613, however, photographing scale factor display is mechanically performed in the photographing lenses. Accordingly, a mechanism for the intermediate ring and a mechanical connecting mechanism for the photographing lenses are complicated.
Furthermore, as will be seen from the above equation (1), since the photographing scale factor is related to the focal point distance of the lenses, the above-described table 1 must be prepared for every kind of lens. Further, data must be referred to as shown in the Table every time the photographing scale factor is changed to perform photographing. This is a very large inconvenience.
Meanwhile, the technical means disclosed in Japanese Patent Laid-Open No. HEI 3-223804 or Japanese Patent Laid-Open No. HEI 3-223817 is one which varies or changes the scale factor while seeing a photographing frame, but is not one which automatically sets the scale factor to an assigned photographing scale factor. Further, a distance from the forward end of the photographing lenses to the subject, a so-called work distance is important information upon considering an illumination of the subject or the like, but display thereof or the like cannot be performed. Moreover, the technical means cannot be used in other lenses.